Ventricular assist device and method

ABSTRACT

A ventricular assist device includes a stent for placement within a cardiac artery and arranged for placement, the stent arranged to have an open configuration defining a flow path, a rotor sized to fit within the stent and arranged for percutaneous placement the flow path, the rotor including a surface disposed about a central portion and angled with respect to the flow path and having a first plurality of magnets. A collar is sized for placement about the cardiac artery and includes a stator. A power source is coupled to the stator, and the stator and the rotor are arranged to rotate the rotor about an axis. A timing control module controls a rotational speed of the rotor. Accordingly, the surface of the rotor is arranged to move blood along the flow path in response to rotation of the rotor.

This application claims the benefit of U.S. Application No. 61/564,264,filed Nov. 28, 2011, and U.S. Application No. 61/566,489, filed on Dec.2, 2011, both of which are hereby incorporated by reference in theirentirety herein.

FIELD OF THE INVENTION

The present invention relates to a ventricular assist device and, morespecifically, to a ventricular assist device suitable for assistingeither the left ventricle, the right ventricle, or both ventricles

BACKGROUND

Left ventricular assist devices are now a therapeutic option in patientswith end-stage dilated cardiomyopathy. Existing device are designed foruse in severe left ventricular failure. These existing devices havelittle adaptability for support of the right sided circulation and, inparticular, are not well-suited for right ventricular failure. Currentdevice designs also tend to be appropriate for patients with dilatedcardiomyopathy, but these devices are not well-suited for use inpatients with restrictive cardiomyopathy. Unfortunately, the outcome hasbeen poor for past attempts to existing devices for restrictivecardiomyopathy.

Additionally, further problems with the present generation of devicesinclude the risk of thrombus formation and the risk of infection, aswell as negative effects of non-physiologic (non-pulsatile) flow.Non-physiologic flow can potentially cause a number of side-effects,including a high prevalence of gastrointestinal and/or cerebralbleeding. The etiology of the gastrointestinal bleeding is in partrelated to the non-physiologic flow, and may also be related to thedepletion of clotting factors within the blood which may be destroyed bysuch a non-physiologic assist device. Some existing devices are known tohave a 30% incidence of clotting factor depletion.

Current devices also may be difficult to use in the setting of an acutemyocardial infarction. In such a situation, the freshly infarctedmyocardial tissue may be friable, particularly if the location is apicalor anterior. Consequently, use of existing devices may not be feasiblebecause of the apical placement of the inflow cannula.

SUMMARY

In accordance with one aspect, a ventricular assist device for a humanheart may comprise a stent sized for placement within a cardiac arteryand arranged for percutaneous placement at a selected location withinthe cardiac artery, with the stent arranged to have an openconfiguration defining a flow path, a rotor sized to fit within thestent and arranged for percutaneous placement at the selected locationand within the flow path, with the rotor including a surface disposedabout a central portion and angled with respect to the flow path, therotor further defining a longitudinal axis and having a first pluralityof magnets. The device includes a collar sized for placement about thecardiac artery at the selected location, with the collar comprising astator having an electrical winding. A power source is provided and isoperatively coupled to the stator, and the stator and the rotor arearranged to interact in response to the application of power from thepower source to the stator to cause the rotor to rotate about thelongitudinal axis. A timing control module is provided and isoperatively coupled to the stator, and is arranged to control arotational speed of the rotor. Accordingly, the surface of the rotor isarranged to move blood along the flow path in response to rotation ofthe rotor.

In accordance with one or more preferred aspects, the collar includes amagnet set and the rotor includes a second plurality of magnets, themagnet set of the collar and the second plurality of magnets of therotor cooperating to control a longitudinal position of the rotor withrespect to the flow path. The selected location can be the aorta, whichallows the device to function as a left ventricular assist device, ormay be the pulmonary artery, which allows the device to function as aright ventricular assist device. Still further, the device may be placedin both the aorta and the pulmonary artery, which allows the device tofunction as a bi-ventricular assist device. Preferably, the selectedlocation or locations may be supravalvular. Still further, the collarmay be adapted for minimally invasive placement about the appropriatevessel or vessels.

The surface of the rotor may be formed by a plurality of blades, thesurface of the rotor may be helical, the surface of the rotor maycomprise a plurality of surfaces, and the surface of the rotor maycomprise any suitable form or shape to permit movement of blood alongthe flow path in response to rotation of the rotor.

Preferably, the timing control module is operatively coupled to a sensorarranged to sense native cardiac rhythms, and the timing module isarranged to control the rotational speed of the rotor in response to thenative cardiac rhythms. The timing control module may further bearranged to control the rotational speed of the rotor between a baselinespeed and a higher speed, wherein the baseline speed is arranged toallow the device to function as a closed valve, and wherein the higherspeed is arranged to move blood along the flow path at a desired flowrate.

Still preferably, one or both of the rotor and the stent are coated withan anticoagulant. The power the power source may be subcutaneous, andmay be arranged for transcutaneous charging.

In accordance with another aspect, a ventricular assist device for ahuman heart may comprise a stent sized for placement within a cardiacartery at a selected location within the cardiac artery and arranged todefine a flow path, a magnetized rotor sized to fit within the stent andat the selected location and within the flow path, the rotor including asurface angled with respect to the flow path and including alongitudinal axis, and a collar. The collar is sized for placement aboutthe cardiac artery at the selected location, with the collar comprisinga stator having an electrical winding. The device includes a powersource operatively coupled to the stator, and the stator and the rotorare arranged to interact in response to the application of power fromthe power source to the stator to cause the rotor to rotate about thelongitudinal axis. A timing control module is provided, and the timingcontrol module is operatively coupled to the stator and is arranged tocontrol a rotational speed of the rotor between a baseline first speedand a higher second speed. The surface of the rotor is arranged to moveblood along the flow path in response to rotation of the rotor.

In accordance with a further aspect, a ventricular assist device for ahuman heart includes a stent, a stator, a rotor, a power source, and acontroller. The stent has a cylindrical stent wall with an inner surfacedefining a flow path and an outer surface configured to be disposedwithin a blood vessel. The stator is disposable within the stent, thestator having a plurality of support struts connected to the stator anddisposable against the inner surface of the stent wall to position thestator within the stent. The rotor includes an outer surface facing theinner surface of the stent wall and defined in part by at least oneblade angled with respect to the flow path, the rotor rotatably mountedon the stator between the inner surface of the stent and the stator. Oneof the rotor and the stator includes a field magnet and the other of therotor and the stator includes windings. The power source is operativelycoupled to the windings, and the controller is operatively coupled tothe power source to selectively control the power source to vary thespeed of the rotor.

It will be recognized that any of the aspects may be combined with ormodified in light of the preferred aspects disclosed herein, as desired.

When assembled in accordance with one or more preferred forms outlinedherein, the device may be placed using a minimally invasive, off-pumpapproach. Epi-aortic magnets may be placed around the ascending aorta orother desired location, while the magnetically suspended (or levitated)rotor or impeller blade is placed in a supravalvular position, above theaortic valve or the pulmonary valve, thus permitting use in eithersevere left ventricular failure of severe right ventricular failure.Known devices appear unsuitable for placement at one or more of theselocations.

By placing the device using a minimally invasive approach in asupravalvular position, the anatomic integrity of the left ventricle orthe right ventricle may not be affected, and there is a lower risk ofcomplications related to disruption of the integrity of the ventriculararchitecture. This may be particularly beneficial in patientsexperiencing cardiogenic shock following acute myocardial infarction, orexperiencing biventricular failure requiring off-pump support tooff-load the ventricle(s).

A rotor or impeller blade may be levitated within the stent. Both may bedeployed separately and sequentially through the groin using standardtechniques with existing methods. The in-stent rotor or impeller may bemounted within the ascending aortic or pulmonary arteries, to supportthe left or right ventricles respectively. The levitation of the rotoror impeller prevents “touch-down” of the blade or blood driving surfaceagainst the wall of the surrounding vessel.

The placement and function of the disclosed device preferably allows themaintenance of pulsatile physiologic flow to augment the natural cardiaccycle of the heart. Preferably, the device achieves phasic blood flowthrough the use of electrical signals to time the pumping action via thetiming control module to augment normal myocardial contractility. Powermay be provided by a pacemaker type power unit implanted subcutaneously.In one preferred form, the device uses a transcutaneous charging system.Additionally, near field communication (NFC) technology could be used toimpart instructions to the timing control module.

The device may function as an aortic or pulmonary valve. The discloseddevice could be considered in place of a mechanical valve incircumstances where there are problems with the native aortic orpulmonary valves when associated with severe cardiac failure of the leftor right ventricles respectively. For instance, in severe aorticstenosis with cardiac failure, the native diseased valve could beremoved at the time of surgery and the device would—in effect —functionas a valve. The same would be true with aortic regurgitation orinfective endocarditis. On the right side of circulation, the devicecould be used in lieu of a pulmonary valve.

The device may assist in the prevention of thrombus or blood clots atthe site of device implantation and within the device mechanism with theuse of certain techniques. This could be accomplished by the use ofsystemic anticoagulation or the use of special coatings (e.g. fibrinogenlike peptide 2), which prevent formation of thrombus on surfaces of therotor and stent in contact with the blood. These features and uses areenumerated and discussed in more detail below.

Another aspect of the disclosed device would be the control of power andsettings using a near field communication system to control the powerrequirements and output, the timing, and/or other settings. Such anapproach may employ wireless cell phone technology, or other suitabletechnology, as a means of communication with the control unit. Thus thecontrol system would not need any sort of cable or wired connection, andprogramming may be accomplished with hand-held devices, such as througha cell phone or other module. The device and its control system would becompletely implantable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational schematic view of a particular assist deviceassembled in accordance with the teachings of the present invention.

FIG. 2 is an enlarged fragmentary elevational view, partly in section,illustrating the rotor, stent, and the collar assembly forming a portionof the device illustrated in FIG. 1.

FIG. 3 is another enlarged fragmentary elevational view, partly insection, and similar to FIG. 2, but illustrating a plurality of magnetscarried by cooperating portions of the stent and the rotor to control alongitudinal position of the rotor relative to the stent and/or the flowpath.

FIG. 4 is an enlarged cross-sectional view of similar to FIG. 2 butillustrating another exemplary form for the rotor, stent, and collarassembly.

FIG. 5 is an enlarged fragmentary elevational view, partly in section,illustrating another exemplary form for a rotor, stator, and stentforming a portion of another assist device assembled in accordance withthe teaching of the present invention.

FIG. 6 is an end view of the device of FIG. 5 with the fins of the rotorremoved to better visualize supports connecting the stator to the stent.

FIG. 7 is a further enlarged fragmentary elevational view, in section,of the rotor, stator, and stent of FIG. 5.

FIG. 8 is an enlarged elevational diagrammatic illustration of theheart, partly in section, and illustrating a device assembled inaccordance with the teachings of the disclosed invention in place at aselected location on the aorta to function as a left ventricular assistdevice.

FIG. 9 is another enlarged elevational diagrammatic illustration of theheart, partly in section, and a device assembled in accordance with theteachings of the disclosed invention in place at a selected location onthe pulmonary artery to function as a right ventricular assist device.

FIG. 10 is a view of the disclosed device implanted in a patient andoperatively coupled to an implantable unit including a power source anda timing control module.

FIGS. 11-14 are schematic illustration of one exemplary method ofpercutaneous placement of portions of the disclosed device at theselected location.

FIG. 15 is another schematic illustration illustrating additionalaspects of exemplary methods for placement of the disclosed device atthe selected location.

FIG. 16 is an enlarged fragmentary elevation view, partly in section,and illustrating one exemplary method of the device according to FIGS.5-7 as it is introduced into the already expanded stent.

FIG. 17 is an enlarged fragmentary elevation view, partly in section,and illustrating the device according to FIGS. 5-7 as it is secured tothe already expanded stent.

FIG. 18 is an enlarged elevational diagrammatic illustration of theheart, partly section, and illustrating a device assembled in accordancewith the teachings of the disclosed invention in place at a selectedlocation on the aorta to function as a left ventricular assist device,as well as a delivery catheter and guide wire used to place the devicethrough a trans-apical route.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, FIG. 1 illustrates a ventricular assistdevice assembled in accordance with the teachings of a disclosed exampleof the present invention and referred to by the reference numeral 10.The device 10 is suitable for use at a selected location within theheart, which may be within either of two different cardiac arteries, aswe explained in greater detail below. The device 10 includes a stent 12(partially obscured in FIG. 1 but illustrated in greater detail at leastin FIGS. 2 and 3). Preferably, stent 12 defines an axis 13 (see FIG. 2)and is sized for placement/to fit within the selected cardiac arterywhich may be, for example, the aorta or the pulmonary artery. By way ofexample, the diameter of the aorta and the pulmonary artery may beapproximately 2.0 to 3.0 cm, with the diameter of each varying fromindividual to individual and even varying for the individual over thelife of the individual, for example. The stent 12 preferably is arrangedfor percutaneous placement at the selected location within the cardiacartery, and is arranged to have an open configuration as shown in FIG. 1in order to define a flow path 14 extending through the stent 12 andhence through the device 10. The device 10 also includes a rotor 16,which also is partially obscured in FIG. 1, but which is illustrated ingreater detail at least in FIGS. 2 and 3.

Referring still to FIG. 1, the rotor 16 also sized to fit within theselected cardiac artery and is also sized to fit within stent 12 anddisposed within the flow path 14. Still preferably, the rotor 16 isarranged for percutaneous placement at the selected location within thecardiac artery. Referring now to FIG. 2, the rotor 16 generally defineda longitudinal axis 18, and fits within the stent 12 in such a fashionthat the rotor 16 can rotate about its axis 18 as will be described ingreater detail below. The rotor 16 further includes a surface 20surrounding a central portion 22, with the surface 20 preferably angledrelative to both the axis 18 and the central portion 22. The rotor 16also includes a plurality of magnets 24 (the magnets are obscured inFIGS. 1 and 2, but are shown in greater detail in FIG. 3).

The device 10 also includes a collar 26 is sized for placement aroundthe selected cardiac artery. As seen in FIGS. 1 and 2, the collar 26includes a stator 28 having one or more suitable electrical windings 30.Referring to FIG. 1, the device 10 further includes a power source 32and a timing control module 34, both of which are operatively coupled tothe stator 28 (and in particular, the windings 30) via a suitable link36. In response to the application of electrical power from the powersource 32 to the stator 28 (windings 30), the stator 28 and certain ofthe magnets 24 on the rotor 16 interact, therefore causing the rotor torotate about its axis 18 within the stent 12. Consequently, by virtue ofthe surface 20 on the rotor 16, the rotor 16 moves blood along the flowpath 14.

Referring now to FIG. 2, the rotor 16 is shown disposed within the flowpath 14 of the stent 12. The rotor 16 includes a first end 38 and asecond end 40, while the stent 12 includes a first end 42 and a secondend 44. The stator 28 also includes a first end 46 and a second end 48.As will be explained in greater detail below with respect to FIG. 3, therotor 16 is suspended, levitated, or otherwise magnetically held inposition or suspended inside the stent 12. The stent 12 is showndisposed immediately inside an arterial wall 50 which, as alluded toabove, may be the wall of either the pulmonary artery or the aorta. Thecollar 26 (and hence the stator 28 and the winding 30) is disposedimmediately outside the arterial wall 50. In the example of FIG. 2, thesurface 20 is a helical surface 52 in which helical flighting extendsoutwardly from the central portion 22, generally between the first and38 and the second end 40 of the rotor 16. As an alternative to thehelical surface 52 shown in FIG. 2, the surface 20 of the rotor 16 maybe carried by one or more blades. Preferably, the blades would becollapsible and therefore suitable for percutaneous delivery.

Referring now to FIG. 3, the magnets 24 of the rotor 16 are shown ingreater detail. The magnets 24 include a first plurality of magnets 54which are disposed around the rotor 16 so as to permit the firstplurality of magnets 54 to interact with the stator 28 (and inparticular the windings 30) to rotate the rotor 16 about its axis 18 inresponse to the application of power as outlined above. The magnets 24also include a second plurality of magnets, including one or moremagnets 58 disposed adjacent the first end 38 of the rotor 16, and oneor more magnets 60 disposed adjacent the second end 40 of the rotor 16.In the example of FIG. 3, the stent 12 also includes one or more magnets62 disposed adjacent the first end 42 of the stent 12, and one or moremagnets 64 disposed adjacent the second end 44 of the stent 12. Themagnets 58, 60 may be ring-shaped so as to extend generally around theaxis 18 of the rotor 16. Similarly, the magnets 62, 64 also beingring-shaped so as to extend generally around the axis 13 of the stent12. The magnets 58, 60, 62 and 64 interact to maintain the longitudinalposition of the rotor 16 within the stent 12, so as to prevent the rotorfrom undesired movement along its axis 18 and along the flow path 14.The magnets 58, 60 may be disposed on an outer surface of the rotor 16,may be disposed under the outer surface of the rotor 16, or may bedisposed in any other suitable fashion. Similarly, the magnets 62 and 64may be disposed on an inner surface, an outer surface, between the innerand outer surfaces of the stent 12, or in any other suitable fashion.Preferably, the rotor 12 is levitated or suspended as explained above insuch a fashion that the outer-most extremities of the rotor 12 areseparated from the inner surface of the stent 12 by a gap 63.

Referring once again to FIG. 1, the device 10 preferably includes asensor 66 which is arranged to sense native cardiac rhythms. The sensor66 is operatively coupled to the timing control module 34 by a suitablelink 68. Consequently, the timing of the pumping action may be arrangedto work in conjunction with the native cardiac rhythms. In one preferredform, the timing control module 34 is arranged to control the rotationalspeed of the rotor between a baseline speed and a higher speed. Thebaseline speed may be zero, or non-zero. There may be power-savingadvantages to maintaining the baseline speed as a non-zero speed. Whenthe rotor 16 is at or near the baseline speed, the rotor 16 mayeffectively function as a closed valve. On the other hand, at the higherspeed the rotor 16 is arranged to move blood along the flow path at adesired flow rate. Still preferably, one or both of the rotor 16 and thestent 12 may be coated with an anti-coagulant. Further, the power source32, the timing control module 34, and the sensor 66 all are preferablysubcutaneous. Still preferably, the power source may be arranged fortranscutaneous charging.

As another alternative, the timing control module 34 may be programmedor otherwise arranged to control the rotational speed of the rotor tocreate a first flow characteristic and a second flow characteristic. Forexample, the control of the rotor may be such that the first flowcharacteristic creates at least a partial reverse flow, which would beopposite the direction of the flow path 14. In accordance with at leastone exemplary form, such a flow characteristic may act to improvecoronary perfusion. The control of the rotor further may be such thatthe second flow characteristic creates a forward flow, which is along,or otherwise in the direction of, the flow path 14. Preferably, by usingthe sensor 66, the rotation of the rotor may be gated with the nativecardiac rhythms, which allows the device 10 to behave in a mannersimilar to the behavior of an intra-aortic balloon pump (IABP), withpositive forward flow as well as at least some reverse flow.

FIG. 4 illustrates an alternative rotor 116. The rotor 116 may besimilar in most respects to the rotor 16 discussed above, and may besuspended and rotated as discussed above. Thus, like components need notbe discussed in further detail. The rotor 116 includes a central portion122 that is wider in the middle and tapers toward each end 138 and 140.A surface 120 of the rotor 116 includes a helical surface 152, and thehelical surface 152 or flighting again extends radially outwardly fromthe central portion 122. In the example of FIG. 4, the helical surfaceextends outwardly from the central portion 122 a first distance adjacenta middle portion of the rotor 116, and extends a second and lesserdistance adjacent the ends 138, 140. As with the example discussedabove, the gap 63 is formed between an outer extent of the flighting orblades, and an inner surface of the surrounding stent. Further,preferably the surface that drives the blood flow (the helicalflighting, blades, or other suitably shaped surface or structure) wouldbe collapsible and therefore suitable for percutaneous delivery. One ofskill in the art, upon reading the present disclosure, will understandthat features of the rotor 16 and the rotor 116 need not be mutuallyexclusive. Instead, one may combine and/or substitute aspects of the tworotors as desired.

FIGS. 5-7 illustrate another embodiment of a ventricular assist deviceassembled in accordance with the teachings of a disclosed example of thepresent invention. The device 200, like the devices 10 discussed inrelation to FIGS. 1-4, is suitable for use and sized for placement/tofit at a selected location (e.g., supravalvular) within the heart, whichmay be either of two different cardiac arteries, or elsewhere in thevasculature. The device 200 includes a stent 202 with a cylindricalstent wall 204 with an inner surface 206 defining a flow path 208extending through the stent 202 (and hence through the device 200) andan outer surface 210 configured to be disposed within a blood vessel212, such as a cardiac artery, as mentioned previously. The stent 202(and in particular the wall 204) may be defined by a metal (e.g.titanium) or other suitable material mesh tube, as is conventionallyknown.

Referring to FIG. 5, the device 200 also includes a stator 220. Unlikethe stator 28 mentioned relative to the device 10, the stator 220 of thedevice 200 is disposable in (and, as illustrated in FIGS. 5-7, isdisposed in) the stent 202. As illustrated in FIG. 7, the stator 220 hasa plurality of support struts 222 each having a first end 224 connectedto the stator 220 and a second end 226 disposable against the innersurface 206 of the stent 202 (and in particular the stent wall 204) toposition the stator 220 within the stent 202. Further, as illustrated inFIG. 7, the stator 220 has an upstream end 228 and a downstream end 230,and the plurality of support struts 222 depend from the downstream end230 of the stator 220. Additionally, as seen best in FIG. 6, the stator220 may include four support struts 222 disposed equidistant about thestator 220. However, the number of struts 222 and their dispositionalong and about the stator 220 is for illustrative purposes only, andnot by way of limitation. According to still further embodiments, thesecond end 226 may be configured to be securely connected to the innersurface 206 of the stent 202.

Returning to FIG. 5, the device further includes a rotor 240. Similar tothe rotor 16, the rotor 240 is sized for placement/to fit within thestent 202 (and hence at the selected location) in such a fashion thatthe rotor 240 can rotate about its axis 242 within the flow path 208.Also similar to the rotor 16, the rotor 240 has an outer surface 244facing the inner surface 206 of the stent wall 204 and is defined inpart by at least one blade (or flighting) 246 angled with respect to theflow path 208. In this regard, it may also be possible to refer to theblade 246 as angled relative to the axis 242 of the rotor 240 as well.The rotor 240 has an upstream end 248 and a downstream end 250 (see FIG.7), and the blade or flighting 246 may be formed on the outer surface244 of the rotor 240 between the upstream and downstream ends 248, 250,but may or may not cover the entire outer surface 244 of the rotor 240between the upstream and downstream ends 248, 250.

The blade or flighting 246 may be collapsible against the outer surface244 of the rotor 240. In particular, the blade 246 may be collapsible tofacilitate delivery to the location of the stent 202. For example, asexplained below, the device 200 may include an introducer jacket, andthe blade(s) 246 may be collapsed against the rotor 240 (an inparticular the outer surface 244) with the jacket disposed about therotor 240. The blades 246 may extend from the outer surface 244 of therotor 240 without the jacket disposed about the rotor 240 as isillustrated in FIGS. 5 and 7.

Unlike the embodiments in FIGS. 1-4, the rotor 240 is not receivedwithin the stator 220. Instead, the rotor 240 is rotatably mounted onthe stator 220 between the inner surface 206 of the stent wall 204 (orstent 202) and the stator 220 as illustrated in FIG. 7. For example, thedevice 200 may include first and second bearings 260, 262 disposedbetween the stator 220 and rotor 240 to rotatably mount the rotor 240 onthe stator 220. The first bearing 260 may be disposed at the upstreamends 228, 248 of the stator 220 and the rotor 240, while the secondbearing 262 may be disposed at the downstream ends 230, 250 of thestator 220 and the rotor 240.

According to a first embodiment, the first bearing 260 may be amechanical pivot. Alternatively, the first bearing 260 may be ahydrodynamic pivot. Further, the first bearing 260 may be a magneticbearing, such as is described above relative to the embodiments of FIGS.1-4 or below relative to bearing 262. Still other alternatives arepossible according to the teachings of the disclosed example of thepresent invention.

Similarly, the second bearing 262 may take on various forms. Asillustrated in FIG. 7, the second bearing 262 may be a magnetic bearing.In this regard, the bearing 262 may include first magnets 264 attachedto the rotor 240 and second magnets 266 attached to the stator 220, thefirst magnets 264 and the second magnets 266 having aligned polaritiessuch that the repulsion between the magnets 264, 266 will suspend thedownstream end 250 of the rotor 240 from and about the downstream end230 of the stator 220. In this regard, the embodiment illustrated inFIGS. 5-7 is similar to that illustrated in FIGS. 1-4, and in particularas explained relative to FIG. 3. For example, as explained relative tothe magnets 58, 60, 62, 64, the magnets 264, 266 may be ring-shaped soas to extend generally around the axis 242 of the rotor 240 (and theaxis of the stator 220 as well). Moreover, the magnets 264, 266 may bedisposed on, in or under a surface of the rotor 240 or stator 220, or inany other suitable fashion. Further magnets may also be included tolimit the axial motion of the rotor 240 relative to the stator 220 if,for example, a hydrodynamic or magnetic bearing is used as bearing 260.

As illustrated in FIG. 7, the rotor 240 may be rotatably mounted on thestator 220 by providing, in addition to the bearings 260, 262, a rotor240 with an elongate, hollow body 270 that defines an enclosed space272. The stator 220 may also have an elongate body 274 that is disposedor received at least partially (almost entirely, as illustrated) withinthe enclosed space 272 of the rotor 240. It will be recognized that thisis merely one example, and not intended to be limiting.

As for the mechanism used to rotate the rotor 240, one of the rotor 240and the stator 220 includes a field magnet and the other of the rotor240 and the stator 220 includes coils or windings. As illustrated inFIG. 5, a power source 280 (similar to the power source 32 illustratedin FIG. 1) may be operatively coupled to the windings, and a controller282 (similar to the timing control module 34 also illustrated in FIG. 1)may be operatively coupled to the power source 280. The controller 282(which may include a processor and associated memory and/or circuitryand may be programmed/assembled to control the power source 280)selectively controls the power source 280 to vary the speed of the rotor240.

In particular, referring to FIG. 7, the rotor 240 includes a fieldmagnet 284, which may be in the form of a permanent magnet, similar tothe magnets 54 of the embodiment illustrated in FIGS. 1-4. Further, thestator 220 includes windings 286, which may be in the form of windingsor coils (e.g., copper coils), similar to the windings 30 of theembodiment illustrated in FIGS. 1-4. In response to the application ofelectrical power from the power source 280, to the windings 286, thewindings 286 interact with the magnet 284, causing the rotor 240 torotate about its axis 242 within the stent 202. Consequently, by virtueof the blade 246 on the rotor 240, the rotor 240 moves blood along theflow path 208.

The discussion of the device 10 is applicable with equal force to thedevice 200 as it relates to the operation of the associated power source280 and controller 282. For example, the controller 282 may beprogrammed to operate the power source 280 to provide a pulsatile flow.As a further example, the controller 282 may be programmed to controlthe rotational speed of the rotor 240 between a baseline speed and ahigher speed. As a still further example, the device 200 may include acardiac sensor 288 operatively coupled to the controller 282, thecontroller 282 being programmed to use the cardiac sensor 288 todetermine native cardiac rhythms, and to control the rotational speed ofthe rotor in response to the native cardiac rhythms.

Other teachings in regard to the power source 32, module 34 and sensor66 of the device 10 may also be applied to the power source 280,controller 282, and sensor 288 of the device 200. For example, the powersource 280 and controller 282 may be arranged for placementsubcutaneously. In fact, the power source 280 may be arranged fortranscutaneous charging, and the controller 282 may be arranged fortranscutaneous programming.

Other teachings applicable to the embodiment of FIGS. 1-4 may also beapplied to the embodiment of FIGS. 5-7. For example, one or more of thestent 202, the stator 220, and the rotor 240 may be coated with ananti-coagulant. One may combine and/or substitute aspects of the devices10, 200 as desired.

Having thus described the structure and operation of the devices 10 ofFIGS. 1-4 and device 200 of FIGS. 5-7, the placement and method ofplacement is now discussed. While much of the discussion relates to thedevices 10, it will be recognized that the discussion applies with equalforce to the embodiments of FIGS. 5-7.

Referring now to FIG. 8, the device 10 is shown disposed about the aortain a supravalvular position in order to assist with left ventricularfailure. On the other hand, and referring to FIG. 9, the device 10 isshown disposed about the pulmonary artery, again in a supravalvularposition, in order to assist with right ventricular failure. The device10 may prove suitable for still other selected locations. Those of skillin the art, upon reading the present disclosure, will understand thatthe teachings of FIGS. 8 and 9 may be combined, thus creating abi-ventricular assist device by placing the device 10 in the aorta asshown in FIG. 8, and by placing another device in the pulmonary arteryas shown in FIG. 9. The device 10 shown in each of FIGS. 8 and 9 mayincorporate either the rotor 16 of FIGS. 2 and 3, or may incorporate therotor 116 of FIG. 4. Alternatively, the device 200 may be used.

Referring now to FIG. 10, the device 10 is shown implanted within thebody and coupled to the power source 32 and the timing control module 34by one or more suitable links, with the power source 32 and the timingcontrol module 34 incorporated into a single, implantable unit.

Referring now to FIGS. 11-15, an exemplary percutaneous placement methodis illustrated. FIG. 11 illustrates percutaneous access to the desiredlocation, in this case the aorta, via the femoral artery. Initially, thestent 12, in a collapsed configuration, is placed at the desiredlocation above the aortic valve using a suitable guide wire and suitableknown techniques as shown in FIG. 12. As shown in FIG. 13, the stent 12is expanded from the collapsed configuration of FIG. 12 to an expandedconfiguration using an inflatable balloon and known techniques. In theexpandable configuration of FIG. 13, stent 12 now defines the suitableflow path 14. Next, as shown in FIG. 14, the rotor 16 is advanced to thedesired location within the stent 12, again using a suitable guide wireand known techniques. The rotor 16 may be expanded from a collapsedconfiguration during delivery to an expanded configuration by, forexample, removing a sheath, or by using other suitable expansiontechniques. The collar 26, as well as the power source 32, the timingcontrol module 34, and the sensor 66 along with all suitable links, maybe implanted using conventional techniques such as thoracoscopy, asillustrated in FIG. 15, or other suitable techniques.

In a similar fashion, the placement of the device 200 is illustrated inFIGS. 16 and 17. In particular, as illustrated in FIG. 16, the stent 202may be selected and placed at the selected location using knowntechniques in a collapsed configuration and then expanded from acollapsed configuration to an expanded configuration also using knowntechniques (e.g., through the use of an inflatable balloon). As is alsoillustrated in FIG. 16, the combination of the stator 220 and the rotor240 may be placed in an introducer jacket, which jacket collapses theblades 246 against the rotor 240. The support struts 222 may also befolded or otherwise collapsed against the stator 220. The introducerjacket is then introduced into the stent 202, and once the struts 222are in place, the jacket may be removed. For example, the removal of thejacket may cause the blades to extend from the outer surface 244 of therotor 240, and places the device 200 in condition for use, asillustrated in FIG. 17. The power source 280, the controller 282, andthe sensor 288, along with all suitable links, may be implanted usingconventional techniques such as thoracoscopy, as is illustrated in FIG.15 relative to device 10, or other suitable techniques and operativelycoupled to the device 200 (e.g., the power source 280 to windings of thestator 220).

When assembled in accordance with an exemplary aspect of the invention,when the device is used for left ventricular support the device may beplaced above the aortic valve and above the origins of the coronaryarteries (for example, approximately 1 cm superior to the level of thesin θ-tubular junction). In such an application, coronary perfusionwould not be affected.

The device may be placed through the 2nd right intercostal space throughan anterior mini-thoracotomy, off-pump, or through an upperhemi-sternotomy or traditional median sternotomy. Preferably, one ormore of the collar, the stent, and the rotor may be collapsible, andthus suitable for minimally invasive placement at the selectedlocation(s). One exemplary a cardiac surgical approach would be a hybridoperating room with the placement of the impeller and stentpercutaneously. Following a median sternotomy or upper hemisternotomy,once the aorta has been cross-clamped and the patient placed oncardiopulmonary bypass, the aorta could need to be incised. The decisionwhether to remove the native aortic valve would be based on itsintegrity and condition. The device would be mounted above the originsof the coronary arteries. The power source to the unit may be epi-aorticand would be threaded through subcutaneously to the location of thepower pack. The device may be mounted on a titanium, or other suitablematerial, mesh stent-like structure, which would be lightweight andextremely strong. The device mechanism would be mounted within that meshwhich would be sized appropriately to fit the aorta. In the case ofpulmonary location, this would need to be placed in the supravalvularposition in the pulmonary artery.

In another exemplary form, the device (whether the device 10 or thedevice 200) may be placed using a trans-apical approach as illustratedin FIG. 18. The feasibility of the trans-apical approach is welldescribed relative to its use for trans-apically delivered aorticvalves. According to such an embodiment, the aorta would not need to beincised, as the device would be inserted through the left ventricularapex via a mini-thoracotomy (left anterolateral incision, through thefifth or sixth intercostal space). In particular, a delivery catheter orguide wire 300 is introduced directly into the left ventricle using themini-thoracotomy, and the catheter or guide wire 300 initially traversesthe aortic valve under the guidance of trans-esophageal echocardiographyand fluoroscopy to the appropriate position (e.g., above the origin ofthe coronary arteries). A sheath 302 may also be delivered to the leftventricular apex to maintain intraventricular access. The device 10, 200may then be delivered through the sheath 302 over the catheter or guidewire 300 into place, first the stent and then the remainder of thedevice (the rotor or the rotor/stator combination, as collapsed withinthe introducer jacket, e.g.). This approach would minimize the risk ofsystemic embolization from a calcified aorta and would also avoidexposing the arterial circulation in candidates at risk of arterialcompromise from embolization.

The exemplary device of FIGS. 1-4 includes the rotor or impeller on amagnetic mount, such that the rotor is therefore magnetically suspendedor levitated as outlined above. As mentioned above relative to theexemplary devices of FIGS. 1-7, the impeller preferably includes acollapsible pumping surface or structure, such as collapsible blades orother suitable surface, which allow for percutaneous as well astrans-apical placement. The impeller may, in effect, function as a“suction” type of system. With each systolic contraction of the heart,the programming within the pacemaker-like timing control module or unitwould activate the pumping action of the device. The rotor would speedup from its low baseline speed to a higher speed based on requirement,thus creating a negative vortex below it which would augment naturalcontractility of the heart as blood exits through the aorta and throughthe device. With diastole, the device would slow down or even stop.Keeping the rotor moving may be beneficial from a power conservationstandpoint. Also, the stopped or very slowly moving rotor preferablyfunctions in a valve-like capacity to prevent backflow of blood throughthe aorta or pulmonary artery and back into the ventricle. With the nextcycle, the procedure would be repeated. The same method of installationand placement of the power source would be employed in the pulmonaryposition for right ventricular augmentation.

Preferably, the timing of the pump function would be optimized toprovide phasic flow which would be coordinated with ventricular systole.In many patients with end-stage heart failure, a dual chamber orbi-ventricular pacemaker is often used to create synchronicity incontraction between the atrial and ventricular chambers. Placement ofthis device would not alter such function. The sensor 68 (or 288)includes electrodes which would be placed on the heart to obtain atrialand ventricular electrograms (the native cardiac rhythms) and this datawould be sent to the timing control module 34 (or controller 282). Thepower source 32 (or 280) preferably is a pacemaker-like power source.The pumping function of the device 10 (or 200) would be timed tocoordinate with the ventricular electrical impulse indicating the onsetof systole. A pressure sensor may also be provided and preferably wouldbe available to detect changes in pressure thus providing additionalinformation. In this way, the device 10 would be able to adapt tochanging needs and changing heart rate conditions. This would result inaugmentation of blood flow in a more synchronous fashion. The timingcontrol module 34 would also have algorithms incorporated to take intoaccount the timing of atrial and ventricular signals and input ofpressure sensor data to indicate when pressure is rising, thus improvingthe timing of augmentation of phasic flow. In effect, the pump wouldincrease its flow based on physiologic need. The mechanism is that thebaseline speed of the impeller increases, thus forcing blood across thedevice at higher velocity and augmenting native cardiac function.

Additionally, there are several possibilities to prevent thrombusformation. In one iteration, systemic anticoagulation with traditionalanticoagulants in the form of warfarin or low molecular weight heparincould be used with use of low dose aspirin as an anti-platelet agent. Inanother iteration, the device could be coated with material thatprevents formation of thrombus. A non-thrombogenic surface wouldtherefore minimize the need for systemic anticoagulation. In anotherpotential iteration, the use of a direct current charge on the device bycoating it with a dielectric and using a specific circuit to distributethe charge could be used (such as that found in PCT Publication No. WO2008/024714 A1). In another iteration the system could be coated withfibrinogen like peptide that would prevent thrombus formation andprevent the need for systemic anticoagulation.

The unit including the power source 32 and the timing control module 34(or power source 280 and controller 282) preferably would be positionedas illustrated in FIG. 9. In one preferred form, the power source wouldbe placed in the infra-clavicular or sub diaphragmatic regions withsubcutaneous wires to the device for power delivery as well as controlof the device. The facility for near frequency communication (NFC) withthe power source and control unit, via means of a cellular device(iphone, android device, blackberry RIM or “smart phone”) would be builtinto the system thus providing a means of wireless programming. The NFCcontrol unit, which the patient would carry would also provide aconstant monitoring system providing information on power settings,cardiac output and display any potential problems which need to beaddressed; default safety algorithms will be deployed and real-time dataalerts will be sent to the on-call cardiology and cardiovascular teamresponsible for the patient from their home setting. The power sourcepreferably would be transcutaneously charged. Therefore, the entiresystem would be completely implantable, with no external leads or wires.Still preferably, wireless cell phone technology or other suitablewireless communication protocols may be used, enabling the relevanthealth care providers to continuously monitor data from the cloud.

The device as described functions in a synchronous fashion to augmentcardiac contractility. Therefore if cardiac standstill occurs, orventricular arrhythmias occur which prevent normal electricalactivation, problems with device function could occur. One iteration ofthe device includes the use of a defibrillator lead which is attached tothe power pack which can be used to sense the presence of ventriculararrhythmias and deliver an appropriate shock to the heart to terminatethe arrhythmia. This would be necessary in order to provide continuedcardiac output. This could be incorporated into the algorithms whichwould be programmed into the device. Atrial arrhythmias should not be asmuch of a problem, provided ventricular rate is maintained.

Because of the supravalvular nature of the device and its lack ofinterference with native cardiac function, it could be used in differentcardiac failure states. In pure left ventricular failure, the valvewould be placed in the supra-aortic position. In pure right ventricularfailure, it would be placed in the supra-pulmonary valve position. Inbiventricular failure, two devices could be employed sitting in theaorta and the pulmonary artery with appropriate power packs for eachfunctioning device. The power packs could be placed in ainfra-clavicular of infra-diaphragmatic location. In pulmonaryhypertension with severe right heart failure, the device could be usedin the supra-pulmonary valve position augmenting the function of thefailing right ventricle. By virtue of its location, the etiology of theheart failure becomes less important. Thus, it could also be used indiastolic dysfunction and restrictive cardiomyopathic states. By simplyaugmenting device function and increasing the revolutions per minuteduring phasic contraction of the heart, the timing of diastolic fillingbecomes less important.

Because of its location, the device would function adequately as a heartvalve in addition to being an assist device. Hence, the native valvescould be removed and the ability to stop or slow down the impellercompletely would prevent backflow of blood and minimize forward flow ofblood during the diastolic phase.

Because of its ability to be located in any major vessel, the devicecould also be used as a peripheral circulatory assist device for severeperipheral vascular disease. In that iteration, it could be placed inthe descending aorta or in the femoral or iliac vessels and thus augmentblood flow to the lower limbs. Similarly, it could be placed in otherlocations within the aorta to augment blood flow in the relevantvascular beds. For instance, in individuals with severe peripheralvascular disease, placement of the device in the infra-renal positionwould augment natural blood flow and increase perfusion of the lowerlimbs. In critical lower limb ischemia, improvement of a proximal bloodflow may allow the ability to treat the lower limb ischemia.

The disclosed device and/or method may additionally prove especiallyuseful or suitable for placement during congenital heart surgery inpatients requiring hypoplastic left heart reconstruction. Those of skillin the art, upon reading the present disclosure, will also find thedisclosed device and/or method useful in other procedures as well.

The disclosed device and/or method may also prove especially adaptablefor certain energy saving or energy providing technology. For example,the device may be adapted to extract and/or use kinetic energy from theheart and/or from the flow of blood, and use that energy to supply atleast a portion of the power requirements of the device. Further, thedevice may be especially suitable for use with bionic fuel cell power,which can extract electrons from blood glucose, thus supplying power tothe device. A more detailed explanation of such bionic fuel celltechnology can be found in Microfabricated Miniature Biofuel Cells withNanoengineered Enzyme Electrodes, by Nishizawa et al. and MiniaturizedMicrofluidic Biofuel Cells, by Nishizawa.

Preferred embodiments of this invention are described herein, includingthe best mode or modes known to the inventors for carrying out theinvention. Although numerous examples are shown and described herein,those of skill in the art will readily understand that details of thevarious embodiments need not be mutually exclusive. Instead, those ofskill in the art upon reading the teachings herein should be able tocombine one or more features of one embodiment with one or more featuresof the remaining embodiments. Further, it also should be understood thatthe illustrated embodiments are exemplary only, and should not be takenas limiting the scope of the invention. All methods described herein canbe performed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate the aspects of the exemplaryembodiment or embodiments of the invention, and do not pose a limitationon the scope of the invention. No language in the specification shouldbe construed as indicating any non-claimed element as essential to thepractice of the invention.

What is claimed is:
 1. A ventricular assist device for a human heartcomprising: a stent having a cylindrical stent wall with an innersurface defining a flow path and an outer surface sized for placementwithin a blood vessel; a stator disposable within the stent, the statorhaving a plurality of support struts connected to the stator anddisposable against the inner surface of the stent wall to position thestator within the stent; a rotor including an outer surface facing theinner surface of the stent wall and defined in part by at least oneblade angled with respect to the flow path, the rotor rotatably mountedon the stator between the inner surface of the stent and the stator, oneof the rotor and the stator comprising a field magnet and the other ofthe rotor and the stator comprising windings; a power source operativelycoupled to the windings; and a controller operatively coupled to thepower source to selectively control the power source to vary therotational speed of the rotor.
 2. The device of claim 1, wherein therotor comprises the field magnet and the stator comprises the windings,the windings operatively coupled to the power source.
 3. The device ofclaim 1, wherein the stator has an upstream end and a downstream end,the plurality of support struts depending from the downstream end andconnected to the stent.
 4. The device of claim 1, further comprising atleast first and second bearings disposed between the stator and therotor to rotatably mount the rotor on the stator, the first bearingdisposed at an upstream end of the rotor and the stator and the secondbearing disposed at a downstream end of the rotor and the stator.
 5. Thedevice of claim 4, wherein the first bearing is a mechanical pivot andthe second bearing is a magnetic bearing and comprises first and secondmagnets, the first magnets attached to the rotor and the second magnetsattached to the stator, the first and second magnets having alignedpolarities.
 6. The device of claim 4, wherein the first bearing is ahydrodynamic pivot and the second bearing is a magnetic bearing andcomprises first and second magnets, the first magnets attached to therotor and the second magnets attached to the stator, the first andsecond magnets having aligned polarities.
 7. The device of claim 4,wherein the first and second bearings are each a magnetic bearing thatcomprises first and second magnets, the first magnets attached to therotor and the second magnets attached to the stator, the first andsecond magnets having aligned polarities.
 8. The device of claim 1,wherein the stator has a elongate body with a mechanical bearing at afirst end and a magnetic bearing and the plurality of support struts ata second end, and the rotor has an elongate, hollow body defining anenclosed space in which the elongate body of the stator is disposed withthe rotor connected to the stator via the mechanical bearing at thefirst end of the rotor and the magnetic bearing at the second end of therotor.
 9. The device of claim 1, wherein the at least one blade iscollapsible against the outer surface of the rotor, and the ventricularassist device comprising an introducer jacket, the blades collapsedagainst the rotor with the introducer jacket disposed about the rotorand the blades extended from the outer surface of the rotor without theintroducer jacket disposed about the rotor.
 10. The device of claim 1,wherein the cylindrical stent wall comprises a metal mesh tube.
 11. Thedevice of claim 1, wherein the controller is programmed to operate thepower source to provide a pulsatile flow.
 12. The device of claim 1,further comprising a cardiac sensor operatively coupled to thecontroller, the controller being programmed to use the cardiac sensor todetermine native cardiac rhythms, and to control the rotational speed ofthe rotor in response to the native cardiac rhythms.
 13. The device ofclaim 1, wherein the controller is programmed to control the rotationalspeed of the rotor between a baseline speed and a higher speed.
 14. Thedevice of claim 1, wherein one or more of the stent, the stator and therotor are coated with an anti-coagulant.
 15. The device of claim 1,wherein the stent, rotor and stator are sized to fit within one of theaorta and the pulmonary artery.
 16. The device of claim 15, wherein thestent, rotor and stator are sized to fit within one of the aorta and thepulmonary artery at a selected location that is supravalvular.
 17. Thedevice of claim 1, wherein the power source and the controller are sizedfor subcutaneous placement.
 18. The device of claim 17, wherein thepower source is arranged for transcutaneous charging.
 19. The device ofclaim 17, wherein the controller is arranged for transcutaneousprogramming.
 20. A method of implanting a ventricular assist device in aheart, comprising the steps of: selecting a stent sized for placementwithin a blood vessel at a selected location within the blood vessel;placing the stent at the selected location in a collapsed configuration;expanding the stent at the selected location to define a flow paththrough the stent; placing a stator within the stent in the flow path,providing a rotor including an outer surface facing an inner surface ofthe stent wall and defined in part by at least one blade angled withrespect to the flow path, the rotor rotatably mounted on the statorbetween the inner surface of the stent and the stator, one of the rotorand the stator comprising a field magnet and the other of the rotor andthe stator comprising windings; operatively coupling a power source tothe windings; and controlling the power source to cause the rotor torotate about a longitudinal axis.
 21. A ventricular assist device for ahuman heart, the device comprising: a stent, the stent sized forplacement within a cardiac artery and arranged for placement at aselected location within the cardiac artery, the stent arranged to havean open configuration defining a flow path; a rotor, the rotor sized tofit within the stent and arranged for percutaneous placement at theselected location and within the flow path, the rotor including asurface disposed about a central portion and angled with respect to theflow path, the rotor further defining a longitudinal axis and having afirst plurality of magnets; a collar, the collar sized for placementabout the cardiac artery at the selected location, the collar comprisinga stator having an electrical winding; a power source operativelycoupled to the stator; the stator and the rotor arranged to interact inresponse to the application of power from the power source to the statorto cause the rotor to rotate about the longitudinal axis; a timingcontrol module, the timing control module operatively coupled to thestator and arranged to control a rotational speed of the rotor; andwherein the surface of the rotor is arranged to move blood along theflow path in response to rotation of the rotor.
 22. The device of claim21, wherein the stent includes a magnet set and the rotor includes asecond plurality of magnets, the magnet set of the stent and the secondplurality of magnets of the rotor cooperating to control a longitudinalposition of the rotor with respect to the flow path.
 23. The device ofclaim 21, wherein the selected location can be both the aorta and thepulmonary artery.
 24. The device of claim 23, wherein the selectedlocation is supravalvular.
 25. The device of claim 21, wherein thesurface of the rotor is formed by a plurality of blades.
 26. The deviceof claim 21, wherein the surface of the rotor is helical.
 27. The deviceof claim 21, wherein the timing control module is operatively coupled toa sensor arranged to sense native cardiac rhythms, and wherein thetiming module is arranged to control the rotational speed of the rotorin response to the native cardiac rhythms.
 28. The device of claim 21,wherein the timing control module is arranged to control the rotationalspeed of the rotor between a baseline speed and a higher speed, whereinthe baseline speed is arranged to allow the device to function as aclosed valve, and wherein the higher speed is arranged to move bloodalong the flow path at a desired flow rate.
 29. The device of claim 21,wherein one or both of the rotor and the stent are coated with ananti-coagulant.
 30. The device of claim 21, wherein the power source isarranged for subcutaneous placement.
 31. The device of claim 30, whereinthe power source is arranged for transcutaneous charging.
 32. Aventricular assist device for a human heart, the device comprising: astent, the stent sized for placement within a cardiac artery at aselected location within the cardiac artery, the stent arranged todefine a flow path; a magnetized rotor, the rotor sized to fit withinthe stent and at the selected location and within the flow path, therotor including a surface angled with respect to the flow path, therotor further including a longitudinal axis; a collar, the collar sizedfor placement about the cardiac artery at the selected location, thecollar comprising a stator having an electrical winding; a power sourceoperatively coupled to the stator; the stator and the rotor arranged tointeract in response to the application of power from the power sourceto the stator to cause the rotor to rotate about the longitudinal axis;a timing control module, the timing control module operatively coupledto the stator and arranged to control a rotational speed of the rotorbetween a baseline first speed and a higher second speed; and whereinthe surface of the rotor is arranged to move blood along the flow pathin response to rotation of the rotor.
 33. The device of claim 32,wherein the stent is shiftable between a collapsed configuration and anexpanded configuration, the collapsed configuration allowingpercutaneous placement of the stent at the desired location, the stentarranged to shift from the collapsed configuration to the expandedconfiguration when the stent defines the flow path.
 34. The device ofclaim 33, wherein the rotor is shiftable between a collapsedconfiguration and an expanded configuration, the collapsed configurationallowing percutaneous placement of the rotor within the stent at thedesired location.
 35. The device of claim 34, wherein the rotor includesa plurality of blades, the blades arranged to expand when the rotor isshifted from the collapsed configuration to the expanded configuration.36. The device of claim 32, wherein the collar and the rotor includecooperating magnet sets, the magnet sets cooperating to control alongitudinal position of the rotor with respect to the stent along theflow path.
 37. The device of claim 32, wherein the selected location canbe both the aorta and the pulmonary artery.
 38. The device of claim 32,wherein the selected location is supravalvular.
 39. The device of claim32, wherein the timing control module is operatively coupled to a sensorarranged to sense native cardiac rhythms, and wherein the timing moduleis arranged to control the rotational speed of the rotor in response tothe native cardiac rhythms.
 40. The device of claim 32, wherein thetiming control module is arranged to control the rotational speed of therotor between a baseline speed and a higher speed, wherein the baselinespeed is arranged to allow the device to function as a closed valve, andwherein the higher speed is arranged to move blood along the flow pathat a desired flow rate.
 41. The device of claim 32, wherein the timingcontrol module is arranged to control the rotational speed of the rotorto create a first flow characteristic and a second flow characteristic,wherein the first flow characteristic creates at least a partial reverseflow, and wherein the second flow characteristic creates a forward flow.42. The device of claim 32, wherein one or both of the rotor and thestent are coated with an anti-coagulant.
 43. The device of claim 32,wherein the power source is arranged for subcutaneous placement.
 44. Thedevice of claim 43, wherein the power source is a battery and isarranged for transcutaneous charging.
 45. The device of claim 32,wherein the timing control module is arranged for transcutaneousprogramming.
 46. The device of claim 32, wherein the collar is adaptedfor minimally invasive placement at the selected location.
 47. A methodof implanting a ventricular assist device in a heart, comprising thesteps of: selecting a stent sized for placement within a cardiac arteryat a selected location within the cardiac artery; placing the stent atthe selected location in a collapsed configuration; expanding the stentat the selected location to define a flow path through the stent;providing a magnetized rotor sized to fit within the expanded stent atthe selected location and within the flow path, and providing the rotorwith a surface angled with respect to the flow path, the rotor furtherincluding a longitudinal axis; placing a collar about the cardiac arteryat the selected location, the collar comprising a stator having anelectrical winding; operatively coupling a power source to the stator;arranging the stator and the rotor to interact in response to theapplication of power from the power source to the stator to cause therotor to rotate about the longitudinal axis; providing a timing controlmodule operatively coupled to the stator and arranged to control arotational speed of the rotor between a baseline first speed and ahigher second speed; and activating the rotor to move blood along theflow path in response to rotation of the rotor.
 48. The method of claim47, wherein the selected location is in a pulmonary artery of the heart,and including directing at least a portion of the flow path toward anartificial lung.
 49. The method of claim 47, wherein the timing controlmodule is arranged to rotate the rotor to create a reverse flow.
 50. Themethod of claim 47, including coupling the timing control module to asensor, the sensor arranged to detect native cardiac rhythms, andarranging the timing control module to rotate the rotor to coincide withthe native cardiac rhythms.